Friction – Slip Sliding Away, or Not?

 Today our students were materials scientists! They explored the forces of friction using a spring scale, a coffee mug, and may have tried several different surfaces that they stuck to the bottom of the mugs. Students needed a steady hand, good teamwork, and keen observational skills. In their experimenting, students discovered two types of friction: static friction, which is the force that opposes setting an object in motion, and kinetic friction, which is the force that opposes keeping an object in motion. They found that although the size of the frictional force could be quite different, depending on the surfaces that were sliding, the static friction for any surface was always greater than the kinetic friction for that surface. They also found that heavier objects experience more friction. Frictional forces are important in engineering too! In our discussion, we also considered when friction was helpful (braking a car or bicycle, walking along without slipping, grabbing hold of an object), and when it was unhelpful (making machinery overheat!) and needed to be minimized. You can challenge your student to spend an hour paying attention to where she/he experiences friction, either as a “good” thing or a “bad” thing.

Fricción: ¿se desliza o no? Hoy, nuestros estudiantes se convirtieron en ingenieros de materiales. Investigaron las fuerzas de fricción usando balanzas de resortes, tazones de café y puede que hayan probado diversos tipos de superficies pegados en la base del tazón. También tuvieron la opción de medir el efecto del peso de un objeto sobre la fricción que experimenta Los alumnos necesitaron manos firmes, buen trabajo en equipo y habilidades de observación. En los experimentos descubrieron dos tipos de fricción: la estática, que es la fuerza que se opone al movimiento cuando el objeto está en reposo; y la cinética, que es la fuerza que se opone al movimiento cuando el objeto está en desplazamiento. Los estudiantes descubrieron que a pesar que el tamaño de la fuerza fricción podía ser muy distinta, dependiendo de la superficie de deslizamiento, la fricción estática para cualquier superficie, siempre fue mayor que la fricción cinética para esa superficie. También observaron que los objetos más pesados experimentan mayor fricción. Las fuerzas de fricción son muy importante para la ingeniería. Durante nuestra discusión, hablamos de la utilidad de ésta, por ejemplo al frenar una bicicleta o automóvil, al caminar sin resbalarse y al agarrar un objeto. También discutimos cuando es inútil y debe minimizarse por ejemplo, si hace que las máquinas se sobrecalientan. Desafíe a su hijo a que observe donde se experimentan las fuerzas de fricción y las clasifique como algo “bueno” o “malo”.

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Lauren Koppel

Lauren earned a Bachelor’s degree with a double major of Biology and Psychology from Clark University, and a Master of Education from the Harvard Graduate School of Education. During her undergraduate years, she worked in a evolutionary neurobiology lab that studied the neural development of annelids (marine worms), with a focus on the sox family of genes. Lauren loves learning about how the world works (including everything from biology to chemistry to engineering), and is passionate about sharing that knowledge and enthusiasm with others. In the past, she has interned at the Museum of Science, where she educated learners of all ages through hands-on activities, games, and experiments. Other science education organizations with which Lauren has worked include The People’s Science, EurekaFest, and Eureka! of Girls Inc. of Worcester. Currently she lives in Boston, where devotes her free time to playing Quidditch, reading sci-fi novels, playing her ukulele, and enjoying all the culinary delights the city has to offer.

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